JP2018069733A - Recording apparatus, and method for control of recording head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve both of keeping heater both end voltages in a recording head constant and suppressing decrease in throughput.SOLUTION: A recording apparatus comprises plural recording elements, a drive circuit which corresponds to each of the plural recording elements and has at least one source follower transistor, and a control part. The control part performs first control for driving the source follower transistor at a fixed pulse width irrespective of the number of the recording elements to be simultaneously driven in the case the number of the recording elements to be simultaneously driven does not exceed a prescribed number, and performs second control for modulating the pulse width and driving the source follower transistor based on the number of the recording elements to be simultaneously driven in the case that the number of the recording elements to be simultaneously driven exceeds the prescribed number.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a printing apparatus and a printing head control method.

  In a recording apparatus that discharges ink by heating ink with an energy generating element (hereinafter referred to as a heater) arranged at the discharge port of the recording head, in order to perform high-speed recording with the recording head, as many heaters as possible are simultaneously used. It is desirable to drive. However, when many heaters are driven simultaneously, the current flowing through the wiring increases. As a result, the voltage drop due to the parasitic resistance of the wiring increases, and the desired thermal energy may not be generated by the heater. The fluctuation of the thermal energy changes the volume of the ink to be ejected, so that the quality of the image is lowered.

  In order to solve such a problem, Patent Document 1 discloses a voltage difference applied to both ends of the heater when the heaters are simultaneously driven as much as possible (full discharge) and when only one bit of the heater is driven (single discharge). Adjusts the wiring resistance according to the distance. Further, with the recent increase in the length of the substrate (for example, 1 inch), in the cited document 2, adjustment by the heater drive circuit configuration (adoption of the source follower configuration) is performed.

  As described above, by adjusting the wiring resistance and making the heater drive circuit (transistor) a source follower configuration, even if there is a voltage fluctuation, the thermal energy given to the heater is made constant, and the volume of ink droplets to be ejected Will also stabilize.

Japanese Patent Laid-Open No. 10-44416 JP 2010-155452 A

  When the heater driving unit is configured as a source follower, the voltage across the heater is always constant. However, since the voltage drop due to the wiring resistance (flexible and recording element substrate) from the main body to the heater must be considered with respect to the heater drive power supply voltage, the voltage across the heater must be designed lower than the heater drive power supply voltage. is there. That is, when the voltage applied to the drain of the transistor is lower than the gate voltage, the voltage supplied to the heater is not constant. It is conceivable that this amount of heat becomes a voltage loss and the recording head is heated more than necessary. Therefore, since it is important to suppress the heat in the recording head as much as possible from the viewpoint of throughput, it has led to a bottleneck to speeding up.

  In order to solve the above problems, the present invention has the following configuration. That is, the recording apparatus includes a plurality of recording elements, a driving circuit corresponding to each of the plurality of recording elements and having at least one source follower transistor, and the number of recording elements that are simultaneously driven does not exceed a predetermined number. In this case, the first control for driving the source follower transistor with a fixed pulse width is performed regardless of the number of recording elements to be driven simultaneously, and the number of recording elements to be driven simultaneously exceeds the predetermined number. And a controller that performs second control for modulating the pulse width based on the number of recording elements that are driven simultaneously to drive the source follower transistor.

  According to the present invention, it is possible to achieve both keeping the voltage across the heater constant and suppressing the decrease in throughput.

1 is a diagram illustrating a configuration example of an ink jet recording apparatus according to the present invention. The figure which shows the example of the control structure of the recording device which concerns on this invention. FIG. 3 is a diagram illustrating an example of a configuration of an inkjet recording head. The figure which shows the structural example of a heater drive circuit. The figure which shows the structural example of a voltage converter circuit. The figure for demonstrating the heater both-ends voltage with respect to the heater simultaneous drive number. The figure for demonstrating a pulse control method. The figure for demonstrating the relationship between the simultaneous drive number of a heater, and a pulse width. The figure for demonstrating a pulse control method. The figure which shows another structural example of the drive circuit of a heater. The figure which shows another structural example of the drive circuit of a heater. The figure which shows another structural example of the drive circuit of a heater. The figure which shows another structural example of the drive circuit of a heater.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  Hereinafter, preferred embodiments of the present invention will be described more specifically and in detail with reference to the accompanying drawings. However, the relative arrangement and the like of the constituent elements described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified.

  In this specification, “recording” (sometimes referred to as “printing”) is not limited to the case of forming significant information such as characters and graphics, but may be significant. Furthermore, it also represents a case where an image, a pattern, a pattern, or the like is widely formed on a recording medium or a medium is processed regardless of whether or not it is manifested so that a human can perceive it visually.

  “Recording medium” refers not only to paper used in general recording apparatuses but also widely to cloth, plastic film, metal plate, glass, ceramics, wood, leather, and the like that can accept ink. Shall.

  Further, “ink” (sometimes referred to as “liquid”) should be interpreted widely as in the definition of “recording (printing)”. Therefore, by being applied on the recording medium, it is used for formation of images, patterns, patterns, etc., processing of the recording medium, or ink processing (for example, solidification or insolubilization of the colorant in the ink applied to the recording medium). It shall represent a liquid that can be made.

  Furthermore, unless otherwise specified, the “recording element” collectively refers to an ejection port or a liquid path communicating with the ejection port and an element that generates energy used for ink ejection.

  Furthermore, unless otherwise specified, the “nozzle” collectively refers to an ejection port or a liquid channel communicating with the ejection port and an element that generates energy used for ink ejection.

  An element substrate (head substrate) for a recording head to be used below does not indicate a simple substrate made of a silicon semiconductor but indicates a configuration in which each element, wiring, and the like are provided.

  Further, the term “on the substrate” means not only the element substrate but also the surface of the element substrate and the inside of the element substrate near the surface. The term “built-in” as used in the present invention is not a word indicating that individual elements are simply arranged separately on the surface of the substrate, but each element is manufactured in a semiconductor circuit. It shows that it is integrally formed and manufactured on an element plate by a process or the like.

  An ink jet recording head (hereinafter referred to as a recording head), which is the most important feature of the present invention, has a plurality of recording elements and a drive circuit for driving these recording elements mounted on the same substrate. For example, the recording head may include a plurality of recording element substrates and a structure in which these element substrates are cascade-connected. Therefore, this recording head can achieve a relatively long recording width. Therefore, the recording head is used not only for a serial type recording apparatus commonly found, but also for a recording apparatus having a full line recording head whose recording width corresponds to the width of the recording medium. Further, the recording head is used in a large format printer using a recording medium having a large size such as A0 or B0 among serial type recording apparatuses.

  Accordingly, first, a recording apparatus using the recording head of the present invention will be described.

[Device configuration]
FIG. 1 is a diagram showing a configuration example of an ink jet recording apparatus (hereinafter referred to as a recording apparatus) to which the present invention can be applied. FIG. 1 shows a form of a general ink jet recording apparatus, and here, a scanning type recording apparatus is shown. Note that the present invention is not limited to this configuration. For example, the present invention can be applied to a recording apparatus including a full-line type ink jet recording head (hereinafter, recording head). Further, the present invention is not limited to the ink jet method and can be applied to other types of recording apparatuses.

  In FIG. 1, the recording apparatus according to the present embodiment includes a paper feed mechanism unit, a paper feed mechanism unit, a paper discharge mechanism unit, a carriage unit, and the like. In the present embodiment, a recording apparatus that performs recording by discharging ink from a discharge port of the recording head 3 to a recording medium based on image information will be described as an example.

  A recording head 3 as recording means is mounted on a carriage 50 that reciprocally moves (main scanning movement). The recording head 3 is detachable by a head set lever 51. Furthermore, the recording head 3 is detachably mounted with one or a plurality of ink tanks 71 corresponding to the inks of the respective colors. Further, the recording head 3 includes a temperature sensor 59 for detecting its own temperature. As the recording medium, various materials such as paper, plastic sheet, cloth, and non-woven fabric can be used as long as sheet-like image recording is possible. In the following description, a sheet-like recording medium is referred to as a “sheet”. Hereinafter, the configuration of the recording apparatus will be described for each mechanism unit.

  The sheet feeding mechanism includes a pressure plate 21 for stacking sheets, a sheet feeding roller for feeding sheets, a separation roller for separating sheets, a return lever for returning sheets to a stacking position, and a movable side for indicating an end of the sheet A guide 26 and the like are attached to the paper feed base 20. A paper feed tray for holding the stacked sheets P is attached to the paper feed base 20 or the exterior of the recording apparatus.

  Regarding the operation of the sheet feeding mechanism, in a normal standby state, the pressure plate 21 is released by a pressure plate cam (not shown), and the separation roller is released by a control cam. Further, the return lever returns the sheet P to the stacking position and is held at a stacking position that closes the stacking port so that the sheet P does not enter the back during stacking. When the paper feeding operation starts from this state, the separation roller first comes into contact with the paper feeding roller by driving the motor. Then, the return lever is released, and the pressure plate 21 contacts the paper feed roller. In this state, feeding of the sheet P is started. The sheet P is limited by a preceding separation unit (not shown) provided in the sheet feeding base 20 and only a predetermined number of sheets P are sent out to the nip portion between the sheet feeding roller and the separation roller. The fed sheet P is separated at the nip portion, and only the uppermost sheet is conveyed (fed).

  When the sheet P reaches a conveyance roller pair composed of a conveyance roller 36 and a pinch roller 37 described later, the pressure plate 21 is released by a pressure plate cam (not shown) and the separation roller is released by a control cam (not shown). The return lever is returned to the loading position by a control cam (not shown). At this time, the sheet that has reached the nip portion between the sheet feeding roller and the separation roller is returned to the stacking position by the return lever.

  The paper feeding mechanism is attached to a chassis 55 made of a bent metal sheet. The sheet feeding mechanism unit includes a conveyance roller 36 that conveys the sheet P and a PE sensor (paper end detection sensor). The conveying roller 36 has a structure in which the surface of the metal shaft is coated with ceramic fine particles, and is attached to the chassis 55 by supporting the metal shaft portions at both ends with bearings (not shown).

  The transport roller 36 is provided with a plurality of driven pinch rollers 37 in contact therewith. The pinch roller 37 is held by the pinch roller holder 30 and is brought into pressure contact with the conveying roller 36 by a pinch roller spring (not shown), thereby generating the conveying force of the sheet P. Here, the pinch roller holder 30 has a rotating shaft pivotally supported by a bearing of the chassis 55 and rotates around the rotating shaft. Further, a paper guide flapper and a platen 34 for guiding the sheet are disposed at the entrance of the sheet feeding mechanism unit to which the sheet P is conveyed. Further, the pinch roller holder 30 is provided with a PE sensor lever (not shown) for transmitting detection of the leading edge and the trailing edge of the sheet P to a PE sensor (not shown).

  The platen 34 is attached to the chassis 55 and positioned. A paper guide flapper (not shown) is fitted with the transport roller 36, can rotate around a sliding bearing portion (not shown), and is positioned by contacting the chassis 55. Further, a recording head 3 as a recording unit that records an image based on image information is provided on the downstream side of the conveying roller 36 in the sheet conveying direction.

  The sheet P is conveyed along the upper surface of the platen 34 as the conveyance roller 36 is rotated by the conveyance motor and the pinch roller 37 is driven to rotate. On the platen 34, a rib serving as a conveyance guide surface (vertical reference position) is formed. The rib manages a gap (distance) between the sheet P and the recording head 3 and regulates cockling (waving) of the sheet P in cooperation with a paper discharge mechanism described later. As a result, image quality deterioration due to cockling of the sheet portion recorded by the recording head 3 is prevented. The conveyance roller 36 is driven by transmitting the rotational force of the conveyance motor composed of a DC motor to a pulley 361 provided on the conveyance roller shaft by a timing belt 541.

  The carriage unit includes a carriage 50 that carries the recording head 3 and reciprocates. The carriage 50 is guided and supported so as to be capable of reciprocating (main scanning) along a guide shaft 52 and a guide rail 54 installed in a direction intersecting (usually orthogonal) with the conveyance direction of the sheet P. The guide shaft 52 constitutes a guide mechanism for guiding the reciprocating movement of the carriage 50. The guide rail 54 also has a function of maintaining the distance (gap) between the recording head 3 and the sheet P at an appropriate value by supporting the rear end portion of the carriage 50. The guide shaft 52 is constituted by a shaft member attached to the chassis 55, and the guide rail 54 is formed integrally with a part of the chassis 55. A thin sliding sheet 53 made of SUS or the like is stretched on a sliding portion of the guide rail 54 with the carriage 50 to reduce sliding noise.

  The carriage unit moves the recording head 3 to the capping position and performs capping with the cap 61 to prevent evaporation of liquid such as ink. The recovery motor 69 operates as a drive source for the cap 61 and the like. Further, the nozzle surface is cleaned by the blade 62. The blade 62 is cleaned by a blade cleaner 66. Further, the recording head 3 discharges ink from the nozzles by the operation of the pump 60 provided in the recovery mechanism unit 6 to reduce ink clogging.

  The paper discharge mechanism is provided with two paper discharge rollers. A spur is pressed against each paper discharge roller so as to be driven and rotated. By rotating each paper discharge roller in synchronization with the transport roller 36, the recorded sheet P is discharged out of the recording apparatus main body. In the present embodiment, the paper discharge roller is attached to the platen 34. The paper discharge roller on the upstream side in the transport direction is configured by providing a plurality of rubber portions (paper discharge roller rubber) on a metal shaft. The first paper discharge roller is driven by the drive from the transport roller 36 being transmitted through an idler gear. The second paper discharge roller 41 has a structure in which a plurality of elastic bodies such as an elastomer are attached to a resin shaft. The second paper discharge roller 41 is driven by a drive transmitted from the first paper discharge roller 40 via an idler gear.

  With the above configuration, the sheet P recorded by the recording head 3 in the carriage unit is sandwiched between the discharge roller and the nip portion of each spur, is discharged out of the recording apparatus main body, and is placed on the discharge tray. The paper discharge tray has a divided structure composed of a plurality of members, and is used by being pulled out during use. Further, the discharge tray is formed so as to increase in height toward the leading end, and both side edges are also formed high in height, thereby improving the stackability of discharged sheets P and The recording surface of the sheet P is prevented from rubbing.

[Control configuration]
FIG. 2 is a block diagram showing a control configuration of the recording apparatus shown in FIG.

  As shown in FIG. 2, the controller (control unit) 600 includes an MPU 601, a ROM 602, a special purpose integrated circuit (ASIC) 603, a RAM 604, a system bus 605, an A / D converter 606, and the like. The ROM 602 stores programs corresponding to various control sequences, necessary tables, and other fixed data. The ASIC 603 controls the pulse width of a signal to be described later. The RAM 604 is used as a development area for image data, a work area for program execution, and the like. A system bus 605 connects the MPU 601, the ASIC 603, and the RAM 604 to each other to exchange data. The A / D converter 606 inputs analog signals from the sensor group described below, performs A / D conversion, and supplies a digital signal to the MPU 601.

  In FIG. 2, a host device 631 is an external information processing apparatus such as a PC that is a source of image data. Image data, commands, statuses, and the like are transmitted and received by packet communication between the host device 631 and the recording device via an interface (I / F) 632. Note that a USB interface may be further provided as the interface 632 separately from the network interface so that bit data and raster data serially transferred from the host can be received.

  The switch group 610 includes a power switch 611, a print switch 612, a recovery switch 613, and the like.

  The sensor group 620 is a sensor group for detecting an apparatus state, and includes a position sensor 621, a temperature sensor 622, and the like. In addition, a photo sensor for detecting the remaining amount of ink is provided.

  The carriage motor driver 633 is a carriage motor driver that drives a carriage motor 635 for reciprocally scanning the carriage 50. The conveyance motor driver 634 is a conveyance motor driver that drives a conveyance motor 636 for conveying the sheet P.

  The ASIC 603 transfers data for driving the heating element (heater for ink ejection) to the recording head 3 while directly accessing the storage area of the RAM 604 during recording scanning by the recording head 3. In addition, this recording apparatus is provided with various display units including LCDs and LEDs as a user interface.

[Recording head configuration]
Details of the recording head 3 according to the present invention will be described with reference to FIG. FIG. 3 is a diagram showing a configuration example of a recording element substrate provided in the recording head 3 according to the present invention.

  On the silicon semiconductor substrate 110 of the recording head 3, an energy generating element array formed by arranging a plurality of heaters 101 that can be energized through wiring is formed. The wiring can be applied to both single-layer wiring and multilayer wiring. A flow path forming member (coating resin material) 111 is disposed on the silicon semiconductor substrate 110, and a plurality of discharge ports 100 corresponding to the plurality of heaters 101 are formed in the flow path forming member 111. The prepared silicon semiconductor substrate 110 is a semiconductor substrate (recording element substrate) such as silicon, and the heater 101 is formed of a material such as tantalum silicon nitride (TASiN).

  Thermal energy generated by the heater 101 is applied to a liquid such as ink to cause a foaming phenomenon in the liquid. Then, ink droplets are discharged from the discharge port 100 by the energy of the foaming. In recent inkjet recording heads, the heater arrangement density is increased and the number thereof is increased in order to improve the recording density (resolution) and the printing speed.

  Although not shown, on the silicon semiconductor substrate 110, a driver for driving each of the heaters 101, a shift register having the same number of bits as the heater, and a latch circuit for temporarily storing print data output therefrom, Is provided. The shift register is for sending serially input image data to the driver in parallel.

  The discharge ports 100 are arranged at a predetermined pitch P along the two discharge port arrays L1 and L2. Further, the discharge ports 100 on the discharge port array L1 side and the discharge ports 100 on the discharge port array L2 side are shifted by a half pitch (P / 2) in the arrangement direction. The heaters 101 are also arranged at the same pitch as the discharge ports 100.

  A common liquid chamber 112 and a hole-shaped ink supply port 500 are formed in the silicon semiconductor substrate 110, and each of the plurality of ejection ports 100 communicates between the silicon semiconductor substrate 110 and the flow path forming member 111. A plurality of ink flow paths (foaming chambers) 300 are formed. The flow path forming member 111 has a wall of the ink flow path 300, and forms the ink flow path 300 by being in contact with the silicon semiconductor substrate 110. The ink supplied from the ink supply member 140 through the common liquid chamber 112 and the ink supply port 500 is introduced into the respective ink flow paths 300. The ink in the ink flow path 300 is foamed by the heat generated by the heater 101 corresponding to the ink flow path 300, and is discharged from the discharge port 100 corresponding to the ink flow path 300 by the foaming energy.

[Heater drive circuit]
FIG. 4 is an explanatory diagram of the heater drive circuit 23. FIG. 4 shows a circuit of one heater 101 for ease of explanation. Therefore, actually, as described above, the silicon semiconductor substrate 110 is provided with the plurality of heaters 101 and the corresponding heater driving circuit 23. One end of the heater 101 is connected to the source terminal of the NMOS transistor 102. The other end of the heater 101 is connected to the source terminal of the PMOS transistor 103. The drain terminals of the NMOS transistor 102 and the PMOS transistor 103 are connected to a power supply wiring (power supply line) 104 and a power supply wiring (ground line) 105, respectively. The output of the voltage conversion circuit 106 shown in FIG. 5A is input to the gate terminal of the NMOS transistor 102. The output of the voltage conversion circuit 107 shown in FIG. 5B is input to the gate terminal of the PMOS transistor 103. A voltage is input from an external power supply to the power supply wirings 104 and 105 via an input terminal provided in the silicon semiconductor substrate 110, and voltages of the high potential side VH and the low potential side GNDH are applied thereto. These potentials are input from the outside via an input terminal, and are the voltage VH of the high voltage side wiring and the voltage GHDH of the low voltage side wiring. The voltage GHDH is a ground voltage in other words. The power supply wiring 104 has a wiring resistance r1, and the power supply wiring 105 has a wiring resistance r2.

  The heater drive circuit 23 includes two voltage conversion circuits 106 and 107. The voltage conversion circuit 106 receives the output signal of the selection circuit 108 and outputs it to the gate of the NMOS transistor 102. The voltage conversion circuit 107 receives the signal HE2 and outputs it to the gate of the PMOS transistor 103. Note that a circuit for generating a signal input to the voltage conversion circuit 106 and the voltage conversion circuit 107 is not limited to this form and configuration.

  A structure of the voltage conversion circuit 106 is illustrated in FIG. The voltage conversion circuit 106 receives the voltage X and GNDH and converts the amplitude of the input signal. The voltage conversion circuit 106 generates a gate voltage for turning on the NMOS transistor 102 based on the voltage X input from the outside of the silicon semiconductor substrate 110. The voltage X is different from the power supply voltage GNDH supplied from the outside of the silicon semiconductor substrate 110 to the drain of the PMOS transistor 103.

  A structure of the voltage conversion circuit 107 is illustrated in FIG. The voltage conversion circuit 107 receives the voltages Y and VH and converts the amplitude of the input signal. The voltage conversion circuit 107 generates a gate voltage for turning on the PMOS transistor 103 based on the voltage Y input from the outside of the silicon semiconductor substrate 110. The voltage Y is a voltage different from the power supply voltage VH supplied to the drain of the NMOS transistor 102. The gate voltage for turning on the PMOS transistor 103 is determined based on the power supply GNDH supplied to the drain of the PMOS transistor 103. The gate voltage for turning on the NMOS transistor 102 is determined based on the power supply VH supplied to the drain of the NMOS transistor 102. The selection circuit 108 outputs a signal corresponding to the image data to the voltage conversion circuit 106. The voltage conversion circuit 106 converts the input signal into a drive voltage (drive signal) for the NMOS transistor 102. On the other hand, the voltage conversion circuit 107 converts the input signal into a drive voltage (drive signal) for the PMOS transistor 103. Thus, the voltage conversion circuits 106 and 107 are circuits that increase the signal amplitude of the input signal.

  FIG. 6 is a graph showing the transition of the voltage across the heater depending on the number of heaters simultaneously driven. In FIG. 6, the vertical axis represents the heater end-to-end voltage [V], and the horizontal axis represents the heater simultaneous drive number [bit]. A graph 151 shows a conventional heater both-end voltage design value. According to the graph 151, the voltage across the heater can be kept constant by a heater driving circuit (hereinafter referred to as a voltage compensation circuit) that supplies a stable voltage to the heater 101 described in FIG. . However, when the heater simultaneous driving number A is exceeded, a voltage drop due to wiring resistance exceeds the range in which the voltage across the heater can be kept constant (hereinafter, voltage compensation range). As a result, the voltage across the heater cannot be kept constant, and the voltage across the heater decreases. The heater simultaneous driving number A is designed by calculating the worst voltage drop value from the wiring resistance to the heater 101 of the entire recording head 3 and the flowing current value depending on the maximum heater simultaneous driving number. For this reason, it is unlikely that the heater simultaneous drive number A will be exceeded in the normal use range, and the voltage across the heater is always kept constant.

  However, in order to compensate for the worst voltage drop value, the voltage across the heater is a value significantly lower than the heater drive power supply voltage (voltage VH) that is actually applied. At this time, if the voltage applied to the drain of the transistor falls below the gate voltage, the voltage supplied to the heater is not constant. Then, it is assumed that the loss becomes heat and the recording head is heated more than necessary.

  Therefore, in the present invention, as shown in the graph 152, the applied voltage setting philosophy (applied voltage in which almost no voltage change occurs under all assumed use environments) is changed from the conventional one, and the applied voltage includes a region exceeding the voltage compensation range. By setting, heat generation due to voltage loss is reduced. Then, in the region beyond the voltage compensation range, the voltage input time is corrected. This solves the above-described problem, that is, coexistence of keeping the voltage across the heater constant and suppressing the decrease in throughput due to temperature rise.

  Specifically, a voltage of B + α is applied to the upper source follower of the heater 101 (the gate of the NMOS transistor 102). Here, the voltage B + α is set to a value that does not cause a voltage loss in the NMOS transistor 102. As a result, the voltage compensation range is set so that the voltage across the heater is constant at the heater simultaneous driving number An as shown in the graph 152 of FIG. 6 in consideration of the voltage drop due to the wiring resistance to the heater 101 of the entire recording head 3. Can't keep up. Here, the region from the heater simultaneous drive number An to the heater simultaneous drive number A in which the voltage across the heater must be kept constant at least is the control region 150 that needs to control the pulse width for driving the heater 101. To do. In the control region 150, the amount that the voltage across the heater cannot be kept constant is corrected by pulse width modulation (hereinafter referred to as PWM control). This makes it possible to keep the voltage across the heater constant until the heater simultaneous drive number A is reached.

  FIG. 8 is a diagram for explaining the relationship between the number of simultaneously driven heaters and the pulse width. In FIG. 8, the vertical axis represents the main pulse width, and the horizontal axis represents the number of heaters simultaneously driven. As shown in FIG. 8A, the pulse width is Pc (constant) when the heater simultaneous drive number is less than An. When the number of heaters simultaneously driven is greater than or equal to An, the pulse width is increased. Thus, if the number of recording elements that are driven simultaneously is equal to or greater than a predetermined number, the pulse width is increased. Note that, as shown in FIG. 8B, the pulse width may be controlled to be increased stepwise as Pc, Pv1, and Pv2.

  Here, the case where voltage compensation is performed up to the heater simultaneous driving number A is described. However, the present invention is not limited to this configuration, and a method may be employed in which the number of simultaneous heater driving is actually increased further than the number A of simultaneous heater driving and PWM control is performed when the region reaches a region outside the voltage compensation range.

  FIG. 7 is a diagram illustrating an example of a PWM control method. In the present embodiment, the heater driving pulse includes a first pulse 91 whose width is controlled depending on the temperature of the recording head 3, a second pulse 93 whose width is controlled depending on the number of heaters simultaneously driven, and The interval 92 is located between the first pulse 91 and the second pulse 93. That is, the heater driving pulse here is in the form of a double pulse of a first pulse (pre-pulse) 91 and a second pulse (main pulse) 93. In addition, although it demonstrated using the example of a double pulse, the single pulse in which only a 2nd pulse exists may be sufficient as needed.

  The control when the heater simultaneous drive number reaches the control region 150 will be described. In the case of the example in FIG. 6, this corresponds to the case where the heater simultaneous drive number reaches An. In this case, as shown in FIG. 7A, the first pulse 91 and the interval 92 are modulated in conjunction with the temperature change, such as the heater driving pulse 153 to the heater driving pulse 154, according to the temperature of the recording head 3. That is, the pulse width of the first pulse 91 is increased according to the temperature change. Note that the temperature of the recording head 3 can be detected by the temperature sensor 59 in the example of the device configuration shown in FIG.

  Next, in order to correct the voltage drop outside the voltage compensation range, the second pulse 93 is changed from the heater driving pulse 153 to the heater driving pulse 155 as shown in FIG. 7B. Modulates in conjunction with. That is, the pulse width of the second pulse 93 is increased as the number of heaters simultaneously driven increases. In the present embodiment, an example linked to the number of heaters simultaneously driven is shown, but the present invention is not limited to this configuration. For example, the configuration may be such that the voltage across the heater is monitored and PWM control is performed when the heater is not kept constant.

  Finally, as shown in FIG. 7C, PWM control is performed such that the heater driving pulse 156 is obtained by combining FIGS. 7A and 7B.

  Note that the PWM control range is a pulse width that falls within the discharge cycle (drive cycle), and it is essential to maintain a voltage level at which the heater 101 can discharge at least. Note that the pulse for driving the heater 101 is not limited to the double pulse, but may be a single pulse as shown in FIG. In the case of FIG. 9, only the second pulse 93 exists in the heater simultaneous drive pulse 901, and the pulse width of the second pulse 93 is controlled to be increased.

  Furthermore, in the present invention, the voltage compensation circuit in which the upper and lower transistors of the heater 101 have a source follower configuration (source follower connection) has been described with reference to FIG. 4, but the present invention is not limited to this. It is also effective in a circuit configuration having a similar action as shown in FIGS. 10A to 10D. Although these configurations have a narrow voltage compensation range, there is an advantage that the circuit scale can be reduced because only one transistor needs to be provided with a voltage conversion circuit. 10A to 10D, the voltage conversion circuit 106 (107) shown in FIG. 4 is omitted for the sake of simplicity.

  In FIG. 10A, the transistors connected to both sides of the heater 101 are NMOS transistors 102. The NMOS transistor 102 connected between the heater 101 and the power supply wiring 104 is a source follower transistor. The NMOS transistor 102 connected between the heater 101 and the power supply wiring 105 is a source ground connection.

  In FIG. 10B, the transistor connected to both sides of the heater 101 is a PMOS transistor 103. The PMOS transistor 103 connected between the heater 101 and the power supply wiring 105 is a source follower transistor. The PMOS transistor 103 connected between the heater 101 and the power supply wiring 104 is a source ground connection.

  In FIG. 10C, the NMOS transistor 102 is connected between the heater 101 and the power supply wiring 104. The NMOS transistor 102 connected between the heater 101 and the power supply wiring 104 is a source follower transistor.

  In FIG. 10D, the PMOS transistor 103 is connected between the heater 101 and the power supply wiring 105. The PMOS transistor 103 connected between the heater 101 and the power supply wiring 105 is a source follower transistor. As described above, the drive circuit for driving the heater includes at least one source follower transistor.

  As described above, when the number of heaters simultaneously driven exceeds a predetermined number, the voltage across the heater can be kept constant by performing PWM control together, and the voltage across the heater can be made higher than before. The head temperature rise can be suppressed with little voltage loss. As a result, it is possible to maintain both the voltage across the heater constant and to suppress a decrease in throughput.

DESCRIPTION OF SYMBOLS 3 ... Recording head, 100 ... Discharge port, 101 ... Heater, 102 ... NMOS transistor, 103 ... PMOS transistor, 106, 107 ... Voltage conversion circuit, 108 ... Selection circuit, 110 ... Silicon semiconductor substrate, 111 ... Channel formation member, 112 ... Common liquid chamber, 140 ... Ink supply member

Claims (8)

A plurality of recording elements;
A drive circuit corresponding to each of the plurality of recording elements and having at least one source follower transistor;
When the number of recording elements to be driven simultaneously does not exceed a predetermined number, the first control for driving the source follower transistor with a fixed pulse width is performed regardless of the number of recording elements to be driven simultaneously to drive simultaneously. A control unit that performs second control for modulating the pulse width and driving the source follower transistor based on the number of recording elements that are simultaneously driven when the number of recording elements exceeds the predetermined number; A recording apparatus.   In the second control, when the number of recording elements to be driven simultaneously is a first value, the control unit drives the source follower transistor with a first pulse width, and the number of recording elements to be driven simultaneously is 2. The recording apparatus according to claim 1, wherein when the second value is larger than the first value, the source follower transistor is driven with a second pulse width longer than the first pulse width.   The recording apparatus according to claim 1, wherein the drive circuit includes an NMOS transistor connected between a power supply line and the recording element.   The recording apparatus according to claim 1, wherein the driving circuit includes a PMOS transistor connected between a ground line and the recording element.   The recording apparatus according to claim 1, wherein the driving circuit includes an NMOS transistor connected between a power supply line and the recording element, and a PMOS transistor connected between a ground line and the recording element. The transistor is driven by a double pulse including a pre-pulse and a main pulse,
The recording apparatus according to claim 1, wherein the control unit controls the width of the prepulse based on the temperature. The recording apparatus includes a recording head,
The recording apparatus according to claim 1, wherein the recording head includes a plurality of recording elements and a transistor corresponding to each of the plurality of recording elements and connected in a source follower. A plurality of recording elements;
A control method for a recording head, which corresponds to each of the plurality of recording elements and has a drive circuit having at least one source follower transistor,
When the number of recording elements to be driven simultaneously does not exceed a predetermined number, the first control for driving the source follower transistor with a fixed pulse width is performed regardless of the number of recording elements to be driven simultaneously,
When the number of recording elements to be driven simultaneously exceeds the predetermined number, second control for modulating the pulse width and driving the source follower transistor based on the number of recording elements to be driven simultaneously is performed. A control method for a recording head.